Determination of Dyestuffs Remaining in Dyeing Processes of Vegetable-Tanned Leathers and Their Removal Using Shavings

This study investigates amounts of acid and metal complex dyes remaining in baths after the dyeing processes of vegetable tanned leathers and their removal using chromium and vegetable shavings as adsorbents. The results indicated that 97-867 mgL(-1) of acid dyes and 15-369 mgL(-1) of metal complex dyes remain at the end of dyeing processes of vegetable-tanned leathers. The adsorption behaviors of chromium and vegetable shavings were investigated toward four acid dyes and four 1:1 metal complex dyes having four different types of metal atoms (Cr, Fe, Cu, Co). Batch adsorption technique was used in adsorption experiments. The effects of time, pH, and adsorbent amount parameters on dye adsorption were investigated. Optimum pH values were pH 2.0 and pH 3.8 for vegetable shavings and chromium shavings, respectively. Adsorption capacities of chromium and vegetable shavings were found to be between 123.5-454.5 mg.g(-1) and 68.0-154.0 mg.g(-1) depending on the type of dye. From the results it was clearly seen that both chromium and vegetable shaving.; could be used as adsorbents for acid and metal complex dyes, while chromium shavings performed better. The experimental data of adsorption isotherms of all dyes fit well to the Langmuir model.